Sphygmomanometer



Oct. 2, 1962 Filed Jan. 10, 1961 E. B. GREENSPAN ETAL SPHYGMOMANOMETER 3Sheets-Sheet 1 INVENTORS 0h/4f0 5. Gees s ay x/o m D6 50m 1170545 Oct.2, 1962 E. B. GREENSPAN ETAL 3,056,401

SPHYGMOMANOMETER Filed Jan. 10, 1961 3 Sheets-Sheet 2 INVENTORS fowmga15. 6 1950151 4 7 BY Jon/y 05 cm QSLE) Arr-019N675 3,656,4tl1SPHYGMGMANQMETER Edward lb. Greenspan and Eohn tie Sela Mosely, New

York, N.Y.; said de Sela Moseiy assignor to said Greenspan Filed 3am.lltl, 1%1, Ser. No. 81,871 Claims. (61. 128-215) This invention relatesto apparatus for measuring blood pressure, and more particularly to aself-recording sphygmomanometer for automatically determining andindicating systolic and diastolic blood pressures.

Generally, a sphygmomanometer is a clinical instrument for measuring themaximum (systolic) and minimum (diastolic) blood pressures indirectly,i.e., without insertion of a pressure reading device into an artery. Itconsists of an inflatable cuff which is wrapped about a patients arm, ananeroid manometer for indicating pressure in the cuff, and a sufllatingbulb equipped with a manually operable bleeder valve. The cuff isinflated until it tightens sufficiently to occlude the artery in thearm, i.e., stop the blood flow therein. The air is then allowed to bleedoff, so that pressure in the cuff falls, and the operator listens to theartery below the cuff with a stethoscope until he hears a pulsing rushof blood commence. The pressure at this point is the systolic pressure.As the air pressure in the cuff continues to fall, a point is reachedwhere the rush of blood becomes inaudible. Pressure at this point is thediastolic blood pressure.

The ordinary method of taking blood pressure as set forth above has manydisadvantages chief among which is the need for a trained and skilledperson to properly use the method which involves interpretation ofarterial sounds sensed through a separate instrument. This isparticularly a problem where repeated rapid blood pressure readings arerequired, for example, during an operation, Where it is highlyundesirable to distract the surgeon and other highly skilled personnel,and Where it is impractical to have present a technician solely for thepurpose of taking blood pressure. Another major drawback is the factthat extraneous noises some of which may emanate from the subjecthimself (bone noises, etc.) can interfere with the taking of the bloodpressure as can, of course, normal outside noises present in a room.Also, the patient must remain very still; and generally the conventionalmethod of taking blood pressure is beset with various inconveniences.

As a result of the foregoing it has been recognized that aself-recording sphygmomanometer automatically responsive to pressure,not sound, would be of very great value to the medical profession.Various attempts to construct such an instrument have been made, but theresults have not been satisfying since the instruments were cumbersome,unreliable, inaccurate, diflicult to use and expensive to produce.

It is a principal object of our present invention to provide anautomatic sphygmomanometer sensitive to the presence and strength ofpulses in an artery and capable of providing accurate readings of thesystolic and diastolic blood pressures.

It is another object of our invention to provide a device of thecharacter described which is direct indicating, i.e., has an output thatis displayed and, if desired, can be automatically recorded.

It is a further object of our invention to provide a device of thecharacter described the readings of which require no interpretation bythe observer other than those which bear on the condition of thesubject.

It is still another object of our invention to provide a device of thecharacter described which is simple and uncomplicated in use.

3,955,4fi1 Patented Get. 2, 1962 It is an additional object of ourinvention to provide a device of the character described which displaysonly the most recent measurement and Will retain this until anothermeasurement is to be made.

It is still a further object of our invention to provide a device of thecharacter described which is insensitive to audible disturbances or tomovements of the patient or manipulation of the patient by medical,technical or other personnel.

It is another object of our invention to provide a device of thecharacter described which causes no discomfort to the patient, i.e., inwhich the cuff need remain inflated for only a minimum amount of time,no more, and usually far less, than with manual taking of bloodpressure.

it is an additional object of our invention to provide a device of thecharacter described which is rugged, long lasting and durable.

it is a further object of our invention to provide a device of thecharacter described which can be produced relatively inexpensively andwhich lends itself to permanent installations, as in laboratories andoperating room, desk installations, as in a physicians ofiice, and toportable forms as for house calls.

Other objects of our invention in part will be obvious and in part willbe pointed out hereinafter.

Our invention accordingly consists in the features of construction,combinations of elements, and arrangements of parts which will beexemplified in the device hereinafter described and of which the scopeof application will be indicated in the appended claims.

In the accompanying drawings in which is shown one of the possibleembodiments of our invention.

FIG. 1 is a broken away front View of an automatic sphygrnornanometerconstructed in accordance with our invention, the same being illustratedin use on an arm;

FIG. 2 is an electric circuit diagram for the sphygmomanometer;

FIG. 3 is an enlarged fragmentary sectional view of the means forconverting systolic air pressure impulses into systolic electricalpulses;

FIG, 4 is an exploded view of the sphygmomanometer;

FIG. 5 is an end view of the sphygmomanometer with the casing removed;

FIG. 6 is a sectional view taken substantially along the line 6-6 ofFIG. 5 and showng the aneroid manometer, i.e., the pressure sensitivemeans, of the sphygmomanomoter; and

FIG. 7 is a sectional view taken substantially along the line 77 of FIG.5.

In general we achieve the several objects of our invention by providinga means such as an inflatable cuff which furnishes a source of airpressure and of air pressure impulses that commence at substantially asubjects systolic pressure and terminate substantially at a subjectsdiastolic pressure. Suitable means is included to sense these pressureimpulses and to transduce them into a train of electric pulses.Furthermore, we include a pressure sensitivity means, such as an aneroidmanometer, which is continually responsive to the air pressure in thecuff and which drives two indicating markers, one for systolic and onefor diastolic pressure. The drive between the pressure sensitive meansand the two indicating markers is elastic, so that if the indicatingmarkers are unrestricted, i.e. unblocked or unrestrained, they willcontinuously indicate the mean prevailing pressure within the cuff. Todenote the systolic and diastolic pressures for any given subject twosuitable blocking means are included one of which is responsive to theinitiation of the train of electric pulses and the other of which isresponsive to the termination of the train of electric pulses. The firstof the blocking means is operative upon actuation thereof to lock thesystolic marker, and the second of the blocking means is operative uponactuation thereof to lock the diastolic marker, so that upon initiationof the train of electric pulses the systolic marker will be resettablyfixed to indicate systolic pressure and upon the cessation of the trainof electrical impulses the diastolic marker will be resettably fixed toindicate diastolic pressure.

In the preferred form of our invention the diastolic marker iscontinuously resettably fixed and freed as the electric pulses repeat,the freeing taking place upon the occurrence of an electric pulse, andthe fixing taking place upon the termination of a pulse, whereby afteroccurrence of the last electric pulse the diastolic marker will remainfixed, subject, of course, to resetting upon reuse of thesphygmomanometer.

Referring now in detail to the drawings, the reference numeral denotes asphygmomanometer constructed in accordance with and embodying ourinstant invention.

One of the elements of the sphygmomanometer is an inflatable cuff 12 ofconventional construction. As is usual, said cuff includes an inflatableelongated hermetically sealed internal casing of an impermeablesheet-like material, such, for instance, as rubber, desirably encased inan external fabric sleeve. The ends of the sleeve include cooperatingrapidly attachable detachable elements such as a hook and eyes (notshown) for enabling the cuff to be circumscribed around and attached toa patients arm in a snug fit thereon when the internal casing isuninflated.

As is customary in inflatable cuffs for sphygmomanometers, the internalcasing has two conduits 14, 16 in communication with the hollow spacecontained therewithin. One of the conduits 14 is secured to a sufflatingsqueeze bulb 18 having an egress check valve (not shown) at the frontend thereof connected with the conduit 14 through a fitting 20. Thesufflating bulb includes an ingress check valve (not shown) at its rearend 22. Hence, when the bulb is deflated, air will be forced therefromthrough the fitting 20 and conduit 14 into the cuff to raise thepressure of the air contained therewithin and, when the bulb isreleased, communication between it and the cuff will be cut off by theegress check valve, and air will flow into the same through the ingresscheck valve. The fitting 20 also is conventional. It includes a bleedervalve. When the handle 24 thereof is in one position the bleeder valveis closed and when the handle 24 is rotated away from closed positionthe bleeder valve will be progressively opened to permit air from thecuff 12 to leak out through it. As is well known, the bleeder valve ismanipulated for reading of blood pressure so as to cause a slowreduction of the pressure of the air in the cuff.

The other conduit 16 transmits the pressure of the air in the cuff tothe reading portion of the sphygmomanometer 10.

Said reading portion is housed in a casing 26 which contains all of theworking parts of the sphygmomanometer with the exception of the cuff,conduits and sufflating bulb.

One of the elements provided within the casing is a means 28 for sensingthe air impulses and transducing them into electrical pulses, i.e. ameans for generating a train of electric pulses in response to a trainof air pressure impulses. Said pulse generating means constitutes ahollow vessel 29 (see FIGS. 1 and 2) which conveniently is composed oftwo halves 30, 32 secured to one another in any suitable manner, as forexample, by a threaded connection. The space within the vessel 29 issubdivided into two chambers 34, 36 by a flexible transverse diaphragm38. It will be apparent that if the pressure within the cuff isintroduced into a first one of these chambers, a momentary fluctuationin such pressure will cause movement of the diaphragm. De-

A sirably, to enhance flexibility of the diaphragm, the same isconcentrically corrugated.

Moreover, to increase the sensitivity of the means 28 for sensing theair pressure impulses it is desirable to introduce into the second ofthe chambers (the balance, i.e. reference, chamber) a mean air pressurewhich is approximately the same as the fluctuating pressure in the firstair chamber, so that the diaphragm only has to be responsive to a changein pressure occasioned by the air pressure impulses, i.e. to a change indifferential pressure. To this end the conduit 16 is connected through aY-fitting 40 to the opposite ends of the vessel 29, and morespecifically, to the two chambers 34, 36. One branch of the Y-fitting 40is connected by a conduit 42 to a nipple 44 communicating with thereference chamber 34, and the other branch of the Y-fitting is connectedby a conduit 46 to a nipple 48 communicating with the pulsing chamber36. The bore extending through the nipple 44 is constricted as at 50',so that changes in air pressure within the conduit 42 will not beimmediately transmitted to the reference chamber 34. Accordingly, thepressure of the air within said reference chamber is, at any time, equalto the mean pressure within the cuff 12. However, the pressure of theair within the pulsing chamber 36 is substantially instantaneouslyresponsive to fluctuations of pressure within the cuff 12, so that ifany air pressure impulses occur within said cuff, they immediately 'willdeflect the diaphragm 38 either toward or away from the referencechamber 34 depending upon whether the momentary change in such airpressure is positive or negative. Thus, if there is a continuous series(train) of air pressure pulses within the cuff 12, the diaphragm 38 willfluctuate in position and in direct response to such air pressureimpulses With no noticeable lag.

At this point we will interrupt the description of the sphygmomanometerto mention certain physical factors which are inherent in the use of theinflatable cuff 12 and of which we take advantage in the constructionand operation of our sphygmomanometer.

When, in ordinary use, a cuff such as the inflatable cuff 12 is wrappedaround a patients limb, usually an upper arm, and the pressure thereinis increased to a pressure greater than the systolic pressure of thepatient, the cuff acts as a constricting tourniquet to occlude arterialflow of blood in the limb. However, because the pressure exerted by thecuff is elastic, each time that a pulse of blood encounters theobstruction of the constriction in the artery occluded by the tourniquetthere will be an ensuing slight rise of air pressure Within the cuffwhich We shall refer to as a supersystolic air impulse. This pressurerise is comparatively small and in an ordinary sphygmomanometer with aneedle indicator manifests itself as a barely noticeable vibration ofthe needle in the range of about /2 mm. and seldom exceeding 2 or 3 mm.

If now the handle 24 of the bleeder valve is manipulated to permit slowleakage of air from the cuff, the constricting pressure will graduallyreduce until it reaches a point where it will permit momentary openingof the artery each time a systolic pulse of blood approaches the cuff.In other words, as soon as the air pressure in the cuff substantiallymatches the systolic blood pressure of the subject a systolic pulse ofblood will flow through the artery beneath the cuff. This flow willslightly reduce the volume of the inflated cuff and thereby temporarilyraise the pressure of the air within the same so as to create amomentary air impulse which air impulse will be transmitted through theconduit 16 to the reading portion of the sphygmomanometer.

Obviously, as the subjects pulse continues to beat, fresh systolic airimpulses will be generated at succes sively lower mean air pressures, sothat there will be a train of air impulses transmitted from the cuff tothe impulse sensing means 28. These impulses are of continuouslydecreasing mean air pressure because the bleeder valve still ispermitting air to leak out of the end.

The amplitude of said pressure impulses, which we shall refer to assystolic air impulses is in the order of 2 mm. and sometimessubstantially higher, e.g., up to 4 mm. However, the systolic airimpulses are of an appreciably greater magnitude than the supersystolicair impulses generated within the cuff at a cuff pressure above thesubjects systolic pressure and therefore may be readily distinquishedfrom the same by the marked difference in degree of movement of theflexible diaphragm 33. Ordinarily, said diaphragm will move at leasttwice as far for a systolic air impulse as for a supersystolic airimpulse.

As the air pressure within the cuff continues to decrease through thebleeder valve a point ultimately will be reached where such pressure isbelow the subjects diastolic pressure. At this time there is asubstantially free flow of blood into the limb and the systolic airimpulses no longer will be generated in the cuff.

To recapitulate, when the air pressure in the cuff is supersystolic,there will be no systolic air impulses generated. When the pressure inthe cuff reaches the patients systolic pressure, a train of systolic airimpulses will be initiated and will continue to be maintained so long asthe pressure Within the cuff is above the patients diastolic pressure.Finally, when the pressure within the cuff reaches the patientsdiastolic pressure the train of systolic air impulses will beterminated. Thus, the diaphragm 38 will vibrate in a systolic magnitudeso long as the pressure within the cuff is between the patients systolicand diastolic pressures.

As thus far described, we have only indicated the physical arrangementwithin the sensing means 28 for procuring mechanical movement responsiveto the train of systolic air impulses, to wit, the diaphragm 38. Saidmeans further includes an arrangement for generating a train ofelectrical pulses in response to such mechanical movement. The latterarrangement includes an electric contact 52 mounted on that side of thediaphragm 38 which faces the reference pressure chamber 34. Desirably,the contact 52 is mounted near the center of the diaphragm where maximummovement prevails. Said contact 52 forms the movable contact of apulsing switch the stationary contact of which is indicated by thereference numeral 54.

In order to utilize the contacts 52, 54 as a repeating electric switch,we either insulate the contact 54 from the upper half "30 which carriesthe same, or insulate the halves 30, 32 from one another, or, as shown,make said upper half 30 of an electrically non-conductive material,e.g., a phenolformaldehyde condensation resin (Bakelite). The other half32 of the vessel 29* is made of an electrically conductive material,e.g., brass.

The stationary contact 54 is mounted within the reference chamber 3 injuxtaposition to the movable contact 52, but spaced therefrom when thediaphragm 38 is unflexed. However, it should be close enough to themovable contact to be engaged thereby upon the occurrence of a systolicair impulse within the pulsing chamber 35.

Conveniently, in order to enable the sensing means 28 better todistinguish between systolic air impulses and supersystolic airimpulses, means is included to vary the spacing between the two contacts52, 54 when the diaphragm 33 is idle. To this end the stationary contact54 is mounted on a toe 56 extending transversely from a leg 58 that islongitudinally slidable in an opening 60 in the upper wall of the casinghalf 38'. The leg 58 is non-circular, i.e., square, and the opening 69is of matching configuration so as to accurately locate the stationarycontact 54 above the movable contact 52. The upper end of the leg do isenlarged, as at a head 62, which is captively but rotatably securedwithin the lower end of an adjusting screw 64 that is threaded into atapped bore 66 in the upper wall of the casing. With this arrangement itmerely is necessary to turn the screw 64 so as to secure any desiredspacing between the two contacts of the pulsing switch. A lead 68extends away from the adiusting screw and a lead 70 extends away fromthe conductive casing half 32. Accordingly, said lead wires will beelectrically connected when the contacts 52, 54 are engaged and will bedisconnected upon the opening of said contacts.

The sphygmomanometer it) further includes, as mentioned earlier, apressure sensitive means continually responsive to the air pressurewithin the cuff and controlling the mechanical positioning of an elementas a function of said pressure.

Said pressure sensitive means comprises an aneroid manometerconstituting a closed chamber 72 having a flexible front wall 74- whichis concentrically corrugated to enhance flexibility. The chamber is inthe form of a pancake so as to obtain a large surface for said flexiblewall and thus make it quite sensitive to internal air pressure.

Access to the chamber is provided by a nipple 76 that is connected by aconduit 78 to one branch of a Y-fitting 8%) the other branch of which isconnected to the Y-fitting 46. The conduit in leads to the Y-fitting 80.

It will be obvious that when air pressure within the cuff 12 increases,the flexible wall 74 of the chamber 72 will bulge outwardly as indicatedby the arrow A, the extent of such movement desirably being anapproximately linear function of said air pressure so that it isconvenient to read the air pressure on a dial having approximatelyuniform graduations.

It is convenient, in order to simplify the operation of oursphygmomanometer 19, to convert the translatory movement of the flexiblewall 74 into a rotary movement which can drive a needle marker. Anysuitabie conversion mechanism can be used for this purpose, one suchmechanism 82 being illustrated herein.

Said conversion mechanism 82 includes an axially rotatable torque bar 34extending diametrically across and in front of the flexible wall 74. Theends of the torque bar are journalled, as at 85, in brackets 86 that areconnected to a stationary vertical frame plate 88. Fixed to andextending rearwardly from the torque bar 3 toward the flexible wall 74is a feeler finger 90 the tip 92 of which is curved horizontally to lieapproximately parallel to the plane of the flexible wall 74. Said tip isadapted to abut, i.e., to touch or follow, the wall 74- and, in thepreferred form of our invention, is slightly offset from the center ofthis wall. It will be appreciated that, with this arrangement, as longas the tip of the finger contacts the wall, in and out movement of thewall will cause a corresponding oscillation of the torque bar 84 about avertical axis.

An actuating rod 94 extends forwardly from the torque bar 84 and isoperationally integral therewith so as to swing with said torque barupon oscillatory movement thereof occasioned by flexion of the wall 74.The stationary plate 88 is provided with an opening 96 to pass saidactuating rod 94. The forward tip of the actuating rod bears against aleg 98 of a gear sector 1% having gear teeth M2. The sector 100 turnsabout a horizontal shaft 164 fixed to and extending forwardly from thestationary plate 88. It will be quite clear that, with the foregoingarrangement, as the wall 74 flexes it will cause a correspondingrotation of the gear sector 100.

The gear teeth 192 mesh with a motion amplifying pinion 106 fast on ahorizontal forwardly extending shaft 198 the rear end of which isjournalled in the stationary plate 88. Thereby, the comparatively smallangular movement of the gear sector 100 occasioned by flexion of thewall 74 will be amplified into a considerable angular movement which isdesirable for easy reading of the sphygmomanometer.

As thus far described the only motion of the flexible Wall '74 that willrotate the pinion 106 and shaft 108 is an outward movement. A retrogrademovement of the wall 74 will not pull back with it the tip 92 of thefeeler finger 91 Moreover, the connection between the actuating rod 94and leg 98 similarly is a simple abutment. To maintain these two pairsof abutting elements in contact with one another we provide a spiraltorsion spring 116 having one end thereof anchored in a post 112 on thestationary plate 88, and the other end thereof anchored to the pinionshaft 1118. Said spring urges the pinion 1115 in a counter-clockwisedirection, as viewed in FIG. 6, so as to bias the leg 98 against the rod94 and also to bias the tip 92 of the feeler finger against the flexibleWall 74. Said spring additionally prevents backlash in the meshingpinion and gear sector. The spring 110 is a comparatively light spring,i.e., a hair spring, and the restraint imposed thereby on the flexion ofthe wall 74 is so slight as to be unnoticeable.

On the front end of the shaft 1138 we mount an indicating needle 114which is readable against a graduated scale 116 on a stationary dial118. This needle 114 will, therefore, when the sphygmomanometer is inuse, furnish to the observer an instantaneous reading of the airpressure within the cuff 12. The needle will show a high pressure whenthe sufi'lating bulb initially is actuated to constrict the cuff on thesubjects arm and will show the progressive decrease in pressure afteropening of the bleeder valve and passage of the cuff pressure firstthrough the systolic and then through the diastolic pressure points ofthe subject.

The sphygmomanometer also includes a systolic pressure needle 121 and adiastolic pressure needle 122 mounted to turn about axes concentric withthat of the shaft 1118 and to be read against the same scale 116 as thatof the cuff air pressure needle 114, although, as will be appreciated,this is a convenience rather than a necessity.

The systolic needle 120 is fast on a sleeve 124 and the diastolic needle122 is fast on a. sleeve 126. The outer sleeve 126 is journalled in afront stationary vertical plate 128 and the inner sleeve 124 istelescopically received and journalled within the outer sleeve 126.Furthermore, the inner sleeve 124 is journalled on the shaft 108 whichextends through the same. The front end of the shaft 108 is journalledin a stationary bracket 130, and the rear end of the shaft 108 isjournalled in a rear stationary plate 132 as well as in the plate 88.Thus, the shaft 1118, the inner sleeve 124 and the outer sleeve 126 aretelescopic and concentric and turn about a mutual, i.e., common, axis ofrotation.

A ratchet, which conveniently is in the form of a gear 134, is fixed tothe inner sleeve 124 where it extends rearwardly beyond the outer sleeveand another ratchet, conveniently in the form of a second gear 136, isfixed to the outer sleeve 126. To maintain the two ratchets in properrelative position we include a spacer sleeve 138.

Suitable elastic means are included independently to bias the systolicneedle 1241 and the diastolic needle 122 to angular orientationsmatching that of the cuff air pressure needle 114. Said means should belight in action so that they can be readily overridden. However, theyshould be positive and sensitive so that they will be reliable andeflicient. For example, said means may comprise biasing springs.

In the case of the systolic needle 120 we have shown the elastic(overridable) means as constituting alight hairpin torsion centeringspring 1411 having a pair of radial legs connected by a helical sectionwrapped about the portion of the shaft 108 protruding forwardly from theinner sleeve 124. One radial leg terminates in a rearwardly extendingbranch 142 that engages the systolic needle 120. The other radial leghas a forwardly extending branch 144 that engages the cuff air pressureneedle 114. For the diastolic needle 122 the elastic (overridable) meanscomprises a light hairpin torsion centering spring 146 having a pair ofradial legs connected by a helical section likewise wrapped about theforwardly protruding portion of the shaft 108. One of the radial legsterminates in a rearward- 1y extending branch 148 that engages thediastolic needle 122 and the other radial leg terminates in a forwardlyextending branch 1511 that engages the cuff air pressure needle 144.

The radial legs of both hairpin centering springs are so mutuallypositioned when said springs are relaxed that the systolic and diastolicneedles 120, 122 will be in alignment with the cuff air pressure needle114 at such time. Hence, as the cuff air pressure needle turns in eitherdirection it will be followed by the systolic needle and the diastolicneedle, unless, of course, movement of either of said needles 120, 122is restrained in a manner which soon will be described.

The hairpin centering springs 140, 146 are very light, so that if eitheror both of the needles 120, 122 is restrained, the needle 114 still isable to move under the influence of the spring or the flexible wall 74.Moreover, if desired, to insure joint movement of all three needles whenthe air pressure in the cuff initially is raised to its high point, wemay provide the cuff air pressure needle 114 with an abutment 151 thatextends rearwardly thereof into the path of travel of both the systolicand diastolic needles. Thereby, as the cuff air pressure needle 114moves to a high reading the abutment 151 will engage the systolic anddiastolic needles to move them along and in alignment with said cuff airpressure needle. Said abutment also serves to prevent oscillation of thesystolic and diastolic needles under the influence of the centeringsprings.

It will be apparent that when the air pressure in the cuff decreases,the systolic and diastolic needles will follow the needle 114 in itsmovement downward around the scale 116. However, as mentionedpreviously, pursuant to our invention suitable means is includedfirstly, to block downward movement of the systolic needle 1211 upon thedetection of the first systolic air impulse by the sensing means 28, andsecondly, to block downward movement of the diastolic needle 122 uponcessation of the train of systolic air impulses. More specifically, assoon will be appreciated, the diastolic needle is locked after eachsystolic air impulse and is released upon the occurrence of each freshsystolic air impulse, so that the needle will be finally locked for anygiven cycle of operations, i.e., for any given subject, upon theoccurrence of the last systolic air impulse sensed.

Adverting now to the means for locking the systolic needle upon thesensing of the first systolic air impulse and the corresponding firstsystolic electrical pulse, for this purpose we provide a stop pawl 152in the shape of an angled lever having a radial portion 154 and anoffset portion 156. The offset portion terminates in a tooth which isthe functioning element of the pawl and is adapted to engage thesystolic ratchet 134. The systolic stop pawl 152 is journalled on ashaft 157 that extends between the parallel plates 128, 132. Saidsystolic pawl is urged into operative engagement with the ratchet 134 byan elongated helical spring 153 having its lower end anchored to theradial portion 154 and its upper end anchored to the stationary plate132 (see FIG. 5).

An unlocking slat 160 mounted on an unlocking shaft 162 is disposeddirectly above the radial portion 154 of the systolic pawl 152. Thereby,if the unlocking shaft 162 is depressed, it will lower the systolic pawlout of engagement with the systolic ratchet and thus leave the systolicneedle free to follow movement of the cuff air pressure needle 114.

Means is included to maintain the unlocking shaft 162 in its depressed(unlocking) position which permits free movement of the systolic ratchet134. Such means comprises an annular buttress groove 164 on the shaft162 which is adapted to cooperate with a detent 166. As long as thedetent 166 engages the flat side of the buttress groove the shaft 162 isprevented from moving upwardly under the biasing influence of the spring158 and of another like spring soon to be described.

The detent 166 is under the control of a solenoid 168. When theactuating coil 170 of said solenoid is energized, it will pull thedetent 166 out of the groove 164 and thereby allow the systolic spring158 to raise the systolic pawl 152 into engagement with the systolicratchet 132.

The shaft 162 includes an unlocking (reset) button 172 protruding abovethe top wall of the casing 26 in order to enable said shaft to bedepressed when the sphygmomanometer is set up for operation.

The means for locking the diastolic needle upon the cessation ofsuccessive systolic air impulses and the corresponding systolicelectrical pulses constitutes a second stop pawl 174 in the shape of anangled lever having a radial portion 176 and an otfset portion 178. Theoffset portion terminates in a tooth which is the functioning element ofthe pawl and is adapted to engage the diastolic ratchet 136. Thediastolic stop pawl 174 is journalled on the same shaft 157 as that onwhich the systolic stop pawl 152 is journalled. Said diastolic stop pawlis urged into operative engagement with the diastolic ratchet 136 by anelongated helical spring 180 having its lower end anchored to the radialportion 176 and its upper end anchored to the stationary plate 128 (seeFIG.

The unlocking slat 160 includes a portion disposed directly above theradial portion 176 of said diastolic pawl 174. Thereby, when the resetbutton 172 is depressed it will lower the diastolic pawl out ofengagement with the diastolic ratchet and thus leave the diastolicneedle 122 free to follow movement of the cuff air pressure needle 114under influence of the centering spring 146. As in the case of thesystolic ratchet, the diastolic ratchet will be maintained free(unlocked) by the detent 166.

A solenoid 182 is included for electrical unlocking (freeing) of thediastolic pawl 174. The armature 184 of the solenoid is connected by alink 186 to the diastolic pawl 174 so that when the actuating coil 188of said solenoid 182 is energized it will depress the tooth of thediastolic pawl to free the diastolic ratchet 136.

For a reason which later will be apparent our sphy momanometer isprovided with a momentary snap switch 190 the actuating element 192 ofwhich is disposed in the path of travel of the radial portion 154 of thesystolic pawl 152. The momentary switch 190 is a single-poledouble-throw switch.

The electric circuit for our sphygmomanometer is illustrated in FIG. 2.The same is comparatively simple and will be seen to include a battery194 (not physically shown) one terminal of which is connected by a lead196 to ground, e.g., to the chassis (the metallic stationary plates andbase of our sphygmomanometer). The battery is sufficiently powerful toenergize the actuating coils of the solenoids 168, 182. The otherterminal of the battery is connected by a lead 198 to one of thenormally open contacts 200 of an ofi-on switch 202 physically mounted ina convenient place, for example, at the top of the casing 26 (see FIG.1). The other contact of the ofi-on switch is connected by the lead 70to the movable contact 52 of the sensing means 28. The stationarycontact 54 of said means is connected by the lead 68 to the blade 204 ofthe momentary switch 190. The normally open contact 206 of the switch190 is connected by a lead 208 to one terminal of the actuating coil 170of the solenoid 168 the other terminal of which is connected by a lead210 to ground. The normally closed contact 212 of the switch 190 isconnected by a lead 214 to one terminal of the actuating coil 188 of thesolenoid 182 the other terminal of which is connected by a lead 216 toground. It thus will be apparent that the solenoids are connected forenergization in parallel with a series circuit including the battery194, the ofi-on switch 202, the contacts 52, 54 and the switch 190, theswitch 190 operating to selectively 10 determine which of the twosolenoids is actuated at any given time.

In describing the operation of our sphygmomanometer, let it be assumedthat the instrument is in the condition which exists after it has read asubjects systolic and diastolic blood pressures. At this time the cuff12 will be deflated and off the subjects arm. The cufi air pressureneedle 114 will be at the lower end of the scale 116 and the systolicand diastolic needles 120', 122 will be at the former subjects systolicand diastolic blood pressures, respectively. The toggle arm of theofi-on switch 202 will be in off position so that the contacts of saidswitch are open. The unlocking shaft 162 and reset button 172 will be intheir uppermost positions.

To prepare our sphygmomanometer for operation, we first depress thereset button 172. 'It will be noted that prior to depression of saidbutton both pawls are held in looking engagement with their associatedratchets by the springs 158, 180 and the switch 190 is not actuated, sothat the blade 204 thereof engages the normally closed contact 212.

When the reset button 172 is depressed the unlocking slat will engagethe radial portions 154, 176 of the systolic and diastolic pawls 152,174 to unlock (free) the two ratchets. The button will be held indepressed condition by engagement between the detent 166 and thebuttress groove 164, the solenoid 168 being idle because the contacts52, 54 are open (said solenoid is biased idle by a spring 169).Immediately upon disengagement of the ratchets the systolic anddiastolic needles 120, 122 will swing into alignment with the cuff airpressure needle 114 at the lower end of the scale 116, being turned tothis position by the centering hair springs 140, 146 and being preventedfrom oscillating by the abutment 151. Moreover, when the radial portion154 of the systolic pawl 152 is depressed to its unlocking position itwill engage the actuating element 192 of the switch 190 to move theswitch blade 204 against the normally open contact 206 and therebyprepare the actuating coil 170 of the solenoid 168 for energization.However, this solenoid will not be energized as yet because the contacts52, 54, as well as the off-on switch 202, are open.

The sphygmomanometer now is ready for operation,

, the cuff 12 is wrapped about a subjects limb and the sufflating bulb18 manipulated to raise the pressure of the air within the cuff. As thispressure is raised the cult air pressure needle 114, followed by thesystolic and diastolic needles, will quickly swing to a high reading onthescale 116, the reading being higher than the patients systolic bloodpressure.

Next the toggle of the oil-on switch is manipulated to close thecontacts 200 thereof. Closure of said contacts connects the battery 194to the contact 52. However, at the time, the contacts 52, 54 are spacedapart since the pressures in the two chambers 34, 36 are substantiallyequal (the supersystolic air impulses are not strong enough to closesaid contacts) and, accordingly, no voltage will be applied to thecontacts of the switch and to the actuating coil of the solenoid 168.

At this time the air pressure in the cuff is high enough to occlude flowof arterial blood and all three needles 114, 120, 122 are in alignment.Next the doctor turns the handle 24 to open the bleeder valve, thuspermitting a slow steady leakage of air to occur with a correspondingslow steady reduction of air pressure in the cuff 12. Accordingly, theair pressure within the chambers 34, 36 gradually drops in pace with thechange of mean air pressure in the cult. There will be a slightvibration of the diaphragm 38 upon the occurrence of each systolic heat,but, because of the occlusion, the ensuing supersystolic air impulse iscomparatively slight and, in any event, smaller than the amount requiredto flex the diaphragm sufiiciently to engage the contact 52 with the 75contact 54.

When the pressure within the cuff drops to the subjects systolicpressure a systolic pulse of blood will flow under the cuff and thiswill create a systolic air impulse in the cuff which will be transmittedto the pressure chamber 36 where it will raise the diaphragm to anextent suflicient to engage the contact 52 with the contact 54. Closureof these contacts will complete the energization circuit from thebattery 194 to the switch 1% the blade of which at the time engages thenormally open contact 206- that has been closed by depression of theunlocking button 172 through the slat 160. Hence, the first systolicelectric pulse will be fed through the actuating coil 170 of thesolenoid 168. This pulse will pull the detent 166 out of engagement withthe buttress groove 164 so as to release the shaft 162. As sOon as therestraining pressure of the shaft is released the biasing spring 158will pull the systolic pawl 152 into engagement with the systolicratchet 134, thereby locking the systolic ratchet and the systolicneedle 120. Accordingly, said needle will register the subjects systolicblood pressure.

The movement of the systolic pawl 152 into locking engagement willrelease the switch 190, so that the blade 204 thereof will engage thenormally closed contact 212 to place the actuating coil 188 of thesolenoid 182 in circuit with the battery 194. It will be appreciatedthat when the detent 166 releases the shaft 162 the biasing spring 180also pulls the diastolic pawl into locking engagement with the diastolicratchet 136, so that the diastolic needle 122 likewise will be locked.However, the systolic air impulse is a momentary one and the contacts50', 52 only are closed momentarily. When they reopen both the systolicand diastolic needles will remain locked, but when said contacts arenext reclosed they thereupon will energize the actuating coil 188 of thesolenoid 182 to pull the armature 184 thereof closed against the idlingspring 183. This shifts the link 186 and pulls down the diastolic pawl172 to momentarily free the diastolic ratchet 136.

In the interim between the two systolic electrical pulses the mean airpressure within the cuff 12 will have dropped and the cuff air pressureneedle 114 will be at a lower point on the scale 116. Hence, when thediastolic ratchet is released, the centering hair spring 146 will swingthe diastolic needle into registry with the cuff air pressure needle 114at its lower position. Then, as the momentary systolic electrical pulseis terminated, the diastolic needle will again be relocked. This actionis repeated continuously, i.e., the diastolic needle is locked, the cuffair pressure needle 114 drops, the diastolic needle is unlocked andrealigned with the cuff air pressure needle, and then it is lockedagain. Eventually, when the cuff air pressure reaches the subjectsdiastolic blood pressure, the systolic air impulses stop and thesystolic electrical pulses terminate, so that the solenoid 182 is notagain actuated and the diastolic needle remains locked at a pressurewhich is substantially equal to the subjects diastolic blood pressure.Further downward movement of the cuff air pressure needle 114 will notbe followed by the diastolic needle.

It will be appreciated that the physical appearance and design of oursphygmomanometer 1!) will depend upon the particular use of any specificinstrument. For eX- ample, said sphygmomanometer may be quite large ifit is intended to be mounted on a wall for use, for instance, inhospitals, or the sphygmomanometer may be of medium size and suitablyhoused for placement on a doctors desk. Still further, oursphygmomanometer may be made quite smallfismall enough to be packed in aphysicians bag, so that it can be carried about with him.

It thus will be seen that we have provided a device which achieves thevarious objects of our invention and is well adapted to meet theconditions of practical use.

As various possible embodiments might be made of our above invention,and as various changes might be made in the embodiment above set forth,it is to be understood that all matter herein described or shown in theaccompanying drawings is to be interpreted as illustrative and not in alimiting sense.

Having thus described our inventoin we claim as new and desire to secureby Letters Patent:

1. A self-recording sphygmomanometer comprising an inflatable cuffhaving bleeder means, pulsing means responsive to the gas pressurewithin the cuff for creating a train of systolic impulses initiating ata Subjects systolic blood pressure and terminating at the subjectsdiastolic blood pressure, a systolic pressure indicator controlled bythe gas pressure within the cuff, a diastolic pressure indicatorcontrolled by the gas pressure within the cuff, means actuated by thepulsing means on the initial systolic impulse of the train to set thesystolic indicator, and means actuated by the pulsing means on the lastsystolic impulse of the train to set the diastolic pressure indicator.

2. A self-recording sphygmomanometer comprising an inflatable cuffhaving bleeder means, a pressure sensitive means continually responsiveto gas pressure in the cuff, pulsing means sensing systolic pressureimpulses in the cuff and creating a train of systolic impulsesinitiating at a subjects systolic blood pressure and terminating at thesubjects diastolic blood pressure, a systolic pressure indicator,overridable means connecting the systolic pressure indicator to thepressure sensitive means so that the systolic pressure indicator will,when unrestrained, indicate the gas pressure in the cuff, a diastolicpressure indicator, overridable means connecting the diastolic pressureindicator to the pressure sensitive means so that the diastolic pressureindicator will, when unrestrained, indicate the gas pressure in thecuff, means actuated by the pulsing means on the initial systolicimpulse of the train to lock the systolic indicator, and means actuatedby the pulsing means on the last systolic impulse of the train to lockthe diastolic pressure indicator.

3. A self-recording sphygmomanometer comprising an inflatable cuffhaving bleeder means, a pressure sensitive means continually responsiveto gas pressure in the cufi, pulsing means sensing systolic pressureimpulses in the cuff and creating a train of systolic impulsesinitiating at a subjects systolic blood pressure and terminating at thesubjects diastolic blood pressure, a systolic pressure indicator,elastic means connecting the systolic pressure indicator to the pressuresensitive means so that the systolic pressure indicator will, whenunrestrained, indicate the gas pressure in the cuff, a diastolicpressure indicator, overridable means connecting the diastolic pressureindicator to the pressure sensitive means so that the diastolic pressureindicator will, when unrestrained, indicate the gas pressure in thecuff, means actuated by the pulsing means on the initial systolicimpulse of the train to lock both indicators, and means momentarilyactuated by the pulsing means on subsequent systolic impulses of thetrain to momentarily unlock the diastolic pressure indicator, wherebythe diastolic pressure indicator will remain locked at the gas pressurein the cuff at the time of occurrence of the last systolic impulse ofthe train.

4. A self-recording sphygmomanometer comprising an inflatable cuffhaving bleeder means, a pressure sensitive means continually responsiveto gas pressure in the cuff, pulsing means sensing systolic pressureimpulses in the cuff and creating a train of systolic impulsesinitiating at a subjects systolic blood pressure and terminating at thesubjects diastolic blood pressure, a systolic pressure indicator,overridable means connecting the systolic pressure indicator to thepressure sensitive means so that the systolic pressure indicator will,when unrestrained, indicate the gas pressure in the cuff, a diastolicpressure indicator, overridable means connecting the diastolic pressureindicator to the pressure sensitive means so that the diastolic pressureindicator will, when unrestrained, indicate the gas pressure in thecuff, means actuated by the pulsing 13 means on the initial systolicimpulse of the train to lock both indicators, and means momentarilyactuated by the pulsing means on each subsequent systolic impulse of thetrain to momentarily unlock the diastolic pressure indicator, wherebythe diastolic pressure indicator will remain locked at the gas pressurein the cuff at the time of occurrence of the last systolic impulse ofthe train.

5. A self-recording sphygmomanometer comprising an inflatable cufihaving bleeder means, pulsing means responsive to the gas pressurewithin the cuff for creating a train of systolic impulses initiating ata Subjects systolic blood pressure and terminating at the subjectsdiastolic blood pressure, means transducing the systolic impulses into atrain of systolic electric pulses, a systolic pressure indicatorcontrolled by the gas pressure within the cuff, a diastolic pressureindicator controlled by the gas pressure within the cuff, means actuatedby the transducing means on the initial systolic electric pulse of thetrain to set the systolic indicator, and means actuated by thetransducing means on the last systolic electric pulse of the train toset the diastolic pressure indicator.

6. A self-recording sphygmomanometer comprising an inflatable cuffhaving bleeder means, a pressure sensitive means continually responsiveto gas pressure in the cuff, pulsing means responsive to the gaspressure in the cuff for creating a train of systolic impulsesinitiating at a subjects systolic blood pressure and terminating at thesubjects diastolic blood pressure, means transducing the systolicimpulses into a train of systolic electric pulses, a systolic pressureindicator, overridable means connecting the systolic pressure indicatorto the pressure sensitive means so that the systolic pressure indicatorWill, when unrestrained, indicate the gas pressure in the cuff, adiastolic pressure indicator, overridable means connecting the diastolicpressure indicator to the pressure sensitive means so that the diastolicpressure indicator will, when unrestrained, indicate the gas pressure inthe cuff, means actuated by the transducing means on the initialsystolic electric pulse of the train to lock the systolic indicator, andmeans actuated by the sensing means on the last systolic electric pulseof the train to lock the diastolic pressure in dicator.

7. A self-recording sphygmomanometer comprising an inflatable cuffhaving bleeder means, a pressure sensitive means continually responsiveto gas pressure in the cuff, pulsing means responsive to the gaspressure in the cuff for creating a train of systolic impulsesinitiating at a subjects systolic blood pressure and terminating at thesubjects diastolic blood pressure, means transducing the systolicimpulses into a train of systolic electric pulses, a cuff gas pressureindicator controlled by the pressure sensitive means, a systolicpressure indicator, overridable means connecting the systolic pressureindicator to the pressure sensitive means so that the systolic pressureindicator will when unrestrained, indicate the gas pressure in the cuff,a diastolic pressure indicator, overridable means connecting thediastolic pressure indicator to the pressure sensitive means so that thediastolic pressure indicator will, when unrestrained, indicate the gaspressure in the cuff, means actuated by the transducing means on theinitial systolic electric pulse of the train to lock the systolicindicator, and means actuated by the sensing means on the last systolicelectric pulse of the train to lock the diastolic pressure indicator.

8. A self-recording sphygmomanometer comprising an inflatable cuffhaving bleeder means, pulsing means responsive to the gas pressurewithin the cuff for creating a train of systolic impulses initiating ata subjects systolic blood pressure and terminating at the subjectsdiastolic blood pressure, means transducing the systolic impulses into atrain of systolic electric pulses, a systolic pressure indicatorcontrolled by the gas pressure within the cuff, a diastolic pressureindicator controlled by the gas pressure Within the cuff, a solenoidactuated by the transducing means an the initial systolic electric pulseof the train to set the systolic indicator, and a solenoid actuated bythe transducing means on the last systolic electric pulse of the trainto set the diastolic pressure indicator.

9. A self-recording sphygmomanometer comprising an inflatable cuffhaving bleeder means, a pressure sensitive means continually responsiveto gas pressure in the cuff, pulsing means responsive to the gaspressure in the cuff for creating a train of systolic impulsesinitiating at a subjects systolic blood pressure and terminating at thesubjects diastolic blood pressure, means transducing the systolicimpulses into a train of systolic electric pulses, a systolic pressureindicator, overridable means connecting the systolic pressure indicatorto the pressure sensitive means so that the systolic pressure indicatorwill, when unrestrained, indicate the gas pressure in the cuff, -adiastolic pressure indicator, overridable means connecting the diastolicpressure indicator to the pressure sensitive means so that the diastolicpressure indicator will, when unrestrained, indicate the gas pressure inthe cuff, a locking means for the systolic pressure indicator, a lockingmeans for the diastolic pressure indicator, means biasing both saidlocking means to locking position, a manually controllable unlockingmeans for rendering the biasing means inoperable, detent means forholding the unlocking means in inoperable position, first actuatingmeans operable by the first systolic electric pulse of the train torender said detent means inoperable so that both locking means becomeoperable, and second actuating means operable by subsequent systolicelectric impulses of the train to momentarily unlock the diastoliclocking means, whereby the diastolic pressure indicator Will remainlocked at the gas pressure in the cuff at the time of occurrence of thelast systolic electric pulse of the train.

10. A self-recording sphygmomanometer as set forth in claim 9 whereincircuit means is included to render the first actuating means operableupon the first systolic electric pulse and the second actuating meansoperable upon the occurrence of subsequent systolic electric pulses.

11. A self-recording sphygmomanometer comprising an inflatable cuffhaving bleeder means, a pressure sensitive means continually responsiveto gas pressure in the cuff, a pressure chamber having a flexible wall,a conduit connecting the interior of the pressure chamber to the cuff,whereby systolic pressure pulses generated in the cuff will pulsate theflexible wall in response to said pressure pulses to produce a train ofsystolic mechanical impulses that initiate at a subjects systolic bloodpressure and terminate at the subjects diastolic blood pressure, asystolic pressure indicator, overridable means connecting the systolicpressure indicator to the pressure sensitive means so that the systolicpressure indicator will, when unrestrained, indicate the gas pressure inthe cuff, a diastolic pressure indicator, overridable means connectingthe diastolic pressure indicator to the pressure sensitive means so thatthe diastolic pressure indicator will, when unrestrained, indicate thegas pressure in the cuff, means actuated by the sensing means on theinitial systolic mechanical impulse of the train to lock the systolicindicator, and means actuated by the sensing means on the last systolicmechanical impulse of the train to lock the diastolic pressureindicator.

12. A self-recording sphygmomanometer as set forth in claim 11 wherein areference pressure chamber is provided on the opposite side of theflexible wall and wherein a conduit connects the reference chamber tothe cuff to provide an average cuff pressure in said reference chamber.

13. A self-recording sphygmomanometer as set forth in claim 12 wherein arestricted passageway is provided between the reference chamber and thecuff to minimize gas pressure pulsations in the reference chamber.

14. A self-recording sphygmomanometer as set forth in claim 13 whereinthe flexible wall has an electric contact operationally integraltherewith, wherein a stationary electric contact is provided near andspaced from the wall contact, wherein circuit means is providedincluding said 75 contacts to transduce the systolic mechanical impulsesinto 1 5 systolic electric pulses, and wherein both actuating means areresponsive to said systolic electric pulses.

15. A self-recording sphygrnornanometer as set forth in claim 14 whereinmeans is provided to vary the position of the stationary contact so asto adjust the spacing between the two contacts.

References Cited in the file of this patent UNITED STATES PATENTS1,594,581 Uchling Aug. 3, 1926 1% Bradford J an. 9, 1940 Williams Apr.4, 1944 Lippitt Aug. 1, 1944 Gilford Mar. 18, 1958 Boucke Mar. 3, 1959Goolkasian Dec. 22, 1959 FOREIGN PATENTS Great Britain Dec. 9, 1929France Aug. 13, 1934

